Abstract
A facile one-pot method is described for the formation of novel heterostructures in which inorganic nanoparticles are homogeneously distributed throughout an inorganic single crystal matrix. Our strategy uses nanoparticles functionalised with a poly(sodium 4-styrenesulphonate)-poly(methacrylic acid) [PNaStS-PMAA] diblock copolymer as a soluble crystal growth additive. This copolymer plays a number of essential roles. The PMAA anchor block is physically adsorbed onto the inorganic nanoparticles, while the PNaStS block acts as an electrosteric stabiliser and ensures that the nanoparticles retain their colloidal stability in the crystal growth solution. In addition, this strong acid block promotes binding to both the nanoparticles and the host crystal, which controls nanoparticle incorporation within the host crystal lattice. We show that this approach can be used to achieve encapsulation loadings of at least 12 wt% copolymer-coated magnetite particles within calcite single crystals. Transmission electron microscopy shows that these nanoparticles are uniformly distributed throughout the calcite, and that the crystal lattice retains its continuity around the embedded magnetite particles. Characterisation of these calcite/magnetite nanocomposites confirmed their magnetic properties. This new experimental approach is expected to be quite general, such that a small family of block copolymers could be used to drive the incorporation of a wide range of pre-prepared nanoparticles into host crystals, giving intimate mixing of phases with contrasting properties, while limiting nanoparticle aggregation and migration.
Highlights
The ability to create functional inorganic materials through the combination of individual components with contrasting but complementary properties is currently receiving considerable attention due to its promise of materials with novel, tailored properties.[1,2] Traditional methods of synthesising inorganic/ inorganic composites such as mechanical mixing and annealing generally lead to poor de nition of microstructure, and greater control can be achieved using more complex processing such as the formation of alternating layers by physical deposition or chemical solution processing.[3]
The PMAA anchor block is physically adsorbed onto the inorganic nanoparticles, while the PNaStS block acts as an electrosteric stabiliser and ensures that the nanoparticles retain their colloidal stability in the crystal growth solution
We have described a facile one-pot method which leads to the occlusion of inorganic nanoparticles within a single crystal matrix
Summary
The ability to create functional inorganic materials through the combination of individual components with contrasting but complementary properties is currently receiving considerable attention due to its promise of materials with novel, tailored properties.[1,2] Traditional methods of synthesising inorganic/ inorganic composites such as mechanical mixing and annealing generally lead to poor de nition of microstructure, and greater control can be achieved using more complex processing such as the formation of alternating layers by physical deposition or chemical solution processing.[3]. We introduce a facile strategy which leads to nanocomposites in which inorganic nanoparticles are uniformly distributed throughout a single crystal matrix with true nano-scale mixing. The method employs functionalised inorganic nanoparticles as simple crystal growth additives, and is based upon prior observations that certain organic additives, ranging from small molecules,[10,11] to nanometer-scale micelles,[12] sub-micron latex particles[13,14] and gels[15,16] can sometimes be occluded within single crystals, depending on the structures of the additives and crystal and the solution conditions. There is as yet little understanding of the design rules governing such occlusion, which has restricted its application to a limited number of systems employing tailor-made
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